The present invention relates to a power reception control device, a power transmission control device, a non-contact power transmission system, a power reception device, a power transmission device, an electronic instrument, and the like.
In recent years, non-contact power transmission (contactless power transmission) which utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, a household appliance (e.g., telephone handset), and the like has been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device using a primary coil and a secondary coil, for example.
When a non-contact power transmission system successively transmits power in a state in which a metallic foreign object (e.g., thin metal sheet) is inserted between a primary coil (transmission coil) and a secondary coil (receiving coil), a magnetic flux passes through the metallic foreign object so that a short-circuit current (eddy current) flows through the metallic foreign object, whereby the metallic foreign object generates heat and reaches a high temperature (e.g., about 100° C.). The user may be burned when the metallic foreign object reaches a high temperature. Moreover, when the product is partially melted due to heat generated from the metallic foreign object, the product may catch fire.
Since instruments are designed to reduce the space in which a foreign object is inserted by minimizing the space between a power transmission device and a power reception device, the above-mentioned problem generally rarely occurs.
However, a situation may be considered in which a malicious person inserts extremely thin metal foil between a power transmission device and a power reception device, for example. Therefore, measures against insertion of a foreign object are indispensable when putting a non-contact power transmission system into practical use.
As technology relating to measures against insertion of a foreign object, technology has been proposed which provides a dedicated sensor which detects a foreign object (JP-A-2001-275280).
In the technology disclosed in JP-A-2006-60909, a secondary voltage detection section and a secondary current detection section (i.e., dedicated sensor) are provided in a secondary-side instrument (e.g., power-receiving-side portable terminal), and information obtained by the dedicated sensor is transmitted from the secondary-side instrument to a primary-side instrument. The primary-side instrument determines whether or not a primary current (current supplied to primary coil) is an overcurrent using the received information, and controls power supply based on the determination result.
According to the technology disclosed in JP-A-2006-60909, since the dedicated sensor which detects insertion of a foreign object is necessary, the number of parts of the secondary-side instrument increases. Therefore, this technology is disadvantageous from the viewpoint of the mounting area and cost. Moreover, signal processing which detects the secondary voltage and the secondary current and determines whether or not the primary current is an overcurrent is considerably complicated. This imposes load on the primary-side instrument and the secondary-side instrument.